Changes In Net Photosynthetic Rate Research Articles

PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS

SUMMARYThe seasonal levels of nitrogenase activity in Peltigera praetextata and P. canina var. rufescens have been examined at 5, 10, 15, 20, 25, 30, 35°C, under 75, 150, 300 and 450 μEinsteins m−2 s−1 illumination and for all levels of thallus moisture content. The results show only a small increase in activity at high light intensities but a marked temperature optimum at 25–30 C in both species. Of outstanding interest however are the very large rate changes occurring throughout the year. The changes are clearly evident at all temperatures and light levels.These results are discussed in relation to concurrent seasonal changes of net photosynthetic rate and the need for experimental design of physiological work in a multivariate framework is strongly emphasized.

Photosynthesis of Tropical Pasture Plants III. Leaf Age

Grass and legume plants were grown under near-optimum conditions in controlled-environment cabinets. Changes in net photosynthetic rate, dark respiration rate, and carbon dioxide transfer resistances during leaf ontogeny, and variability between leaves on grass tillers and legume runners were studied under controlled conditions in an open gas analysis system.